Fenestrations (segmental duplications) of the intracranial arteries are rare anomalies that have been associated with aneurysms. Fenestrations of the supraclinoid ICA are extremely rare, with only a few reported cases. We present a supraclinoid ICA fenestration, which on axial CTA images initially mimicked an aneurysm, but was correctly delineated as a fenestration on multiplanar reformatted and 3D reconstructed images. Confirmation was made with conventional angiography. To our knowledge, this represents the first time that this rare variant has been identified with cross-sectional imaging. A review of the literature including proposed embryology is provided.